Because the machine tool is characteristic of small volume, low price and capable of being connected to various kinds of application tools, such as grinding discs, emery wheel machines, drilling machines and electric wrenches, it is popular for the operator to rapidly perform the work. In addition to the electric tool driven by electricity, the machine tool also includes the pneumatic tool driven by air pressure.
Currently, the common used machine tool, such as the grinding machine, is disclosed in R.O.C. Patent No. M261316. The machine tool mentioned above mainly includes a main body, a grip portion extended from the main body, a trigger button mounted on the grip portion, a control lever contacting with the trigger button and pivotally mounted thereon, a motor held inside the main body, and a tool shaft connected to the motor. Therefore, when the operator presses the control lever to push the trigger button, the motor and the tool shaft can be driven to operate, and thus drive an action element connected with the tool shaft to rotate and to process a workpiece.
However, as operating the machine tool described above, mostly the operator presses one end of the control lever by the front part of the palm and hold the main body of the machine tool by the fingers, so that the rear part of the palm is suspended, thereby fatiguing the operator's hand easily after a long period of time, and even the muscles or joints become ill and feel pain.
For solving this problem, a machine tool which can support the hand of the operator has been developed, as disclosed in US publication No. 2010/0180714. In this prior art, the disclosed machine tool is similar to the traditional one in which a control lever is pivotally mounted thereon, especially the control lever forms a fore end part and a rear end part at two ends of the pivot location. When in use, the fore end part of the control lever is pressed by the front part of the palm of the operator with the rear end part of the control lever is butted by the rear part of the palm of the operator, so as to support the hand during operation.
However, the operation described above is similar to a seesaw, as shown in FIG. 1 and FIG. 2. When the rear part of the palm butts the rear end part 103 of the control lever 101, the fore end part 102 of the control lever 101 is lifted due to lever principle, so that the machine tool 100 cannot operate normally (as shown in FIG. 1). When the front part of the palm presses the fore end part 102 of the control lever 101, the rear end part 103 of the control lever 101 also is lifted due to lever principle, so that the hand of the operator is propped up by the rear end part 103, thereby losing the support (as shown in FIG. 2). Therefore, this prior art still cannot provide proper support for the hand of the operator while the control lever 101 being pressed to operate the machine tool 100.